The research program has continued to use protein studies through chemical semisynthesis to obtain correlates between the primary structure of proteins and their higher order properties of folding and resultant biological function. X-ray crystallographic studies have progressed on two semisynthesis products, (4-F-His 12, des 16-20)SRNaseS' and (Ala 1,3,9,11,14,15)SRNasesS'. The study of these analogues of bovine pancreatic ribonuclease has provided insight into the mode whereby sequence on the amino terminal region of this enzyme promotes conformation and catalytic function.